Wow. This actually isn't a crack!fic idea, but I have no idea if I'd ever write it.
Idea: In a world where Ed never managed to get Al's body back, and where the homunculus destroyed Amestris before they could stop them, Ed discovers a way to get a second chance.
Time Travel, Ed/Ed pairing.
I want to read this, but I'm no good with complicated storylines. --cries-- This fic idea is probably going to be shelved.